1. Field of the Invention
This invention relates to protective waterproofing membranes. More specifically the present invention is directed to a bituminous waterproofing sheet material having at least one major surface coated with a non-tacky polymeric coating composition. The polymeric coating composition is capable of adhering to freshly poured concrete surfaces and to the cured concrete substructure, and also provides a protective coating during storage and application of the sheet material.
2. Description of the Prior Art
It is known that concrete surfaces and the like can be sealed in a waterproof manner by forming or applying thereon a membrane of a bituminous composition such as asphalt, tar, pitch, or other material which is substantially impermeable to moisture and water vapor. Preformed rubberized asphalt sheet-like materials useful for this purpose are well known. Examples of these materials are disclosed in U.S. Pat. Nos. 3,741,856; 3,853,682, 3,900,102 and 4,215,160. These waterproofing materials have a laminate structure comprising a support sheet having at least one major surface coated with a membrane of a bituminous composition. The bituminous composition has adhesive properties which render it adherent to the support sheet and to the substructure, such as a concrete slab, to which it is applied.
The laminated structures currently available are supplied in the form of rolls. In this form, the laminated structure further comprises a flexible release sheet, such as in the form of a siliconized paper, positioned adjacent to the surface of the bituminous membrane which after removal of the release sheet will eventually be placed in contact with a concrete substructure. This release sheet is needed prior to application to prevent the adhesive membrane from adhering to the sheet immediately adjacent thereto and to protect the adhesive membrane layer from various forms of degradation. This release sheet must be removed to expose the adhesive membrane when applying the waterproofing sheet material to the substructure.
This type of waterproofing sheet material is normally applied after the concrete substructure has been formed. Usually these substructures, such as building foundations, are situated with sufficient space around their perimeter to allow the application of these waterproofing sheets. However, in urban locations, as well as elsewhere, structures are built closely between existing foundations. In fact, to maximize the utility of the land, new buildings are often built directly adjoining the existing ones. Thus, there is no room to apply an external waterproofing sheet. In such situations it is advantageous to pre-apply the waterproofing material in a manner to have it become an integral part of the part of the ultimately formed concrete substructure formation. Typically, this is done by applying the waterproofing material to an outer concrete form, known as lagging.
However, the conventional laminated structure of the bituminous waterproofing sheet material and release sheet presents problems of removal and disposal of the release sheets. This is particularly true when re-bars and inner concrete forms are placed in front of the lagging prior to casting the concrete.